The present invention relates to the art of glass manufacture. More specifically, the present invention provides a novel method and apparatus for blending and mixing an additive into molten glass as it is conveyed through a forehearth channel or the like.
An additive such as frit or batch when added to a molten host glass composition extracts heat from the host. The additive's temperature is thus elevated to its melting point. As the additive temperature rises the host temperature correspondingly decreases. Since the rate of heat transfer is a function of the temperature difference between the heat supplying mass and the mass receiving heat, the rate of heat transfer from host to additive asymptotically approaches zero as the additive approaches the host temperature.
Such a decreasing heat transfer rate is undesirable when the time allowed for blending and homogenizing the host additive mixture is relatively short. Further, extraction of heat by the additive from the host may cause inhomogenities and discontinuities frequently referred to as seeds, stones, striae or mares tails.
Various methods and apparatus for achieving mixing, blending and homogenization have been developed in the past and through advances have been made, most methods still have certain short comings ranging from incomplete mixing to too violent a mixing whereby the very defects, which are intended to be eliminated are in fact exaggerated and increased.